• TalkBass has been independent since 1998. Add your voice.
    Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
    Join free Log in
    Want zero display ads or expanded classifieds tools? Compare plans.

Weird biamp experience

Triad

Triad

Commercial User
Jul 4, 2006
1,695
293
Europe
Disclosures
Builder
#1
Hello! I have a Trace Elliot GP12X (model with crossover) and several cabs. I also have a pair of old Hughes&Kettner 3ways PA cabs (15", 8" and tweeter). They sound good and are big enough to work well with bass.
I played thru these cabs a few times but last time I wired them in biamp just for fun and found out they sound "better": better lows and don't seem to be any quieter than in "stereo"?!
The whole thing doesn't make sense: they have crossovers so when I biamp I should use something like the 15" on one and the mid/tweeter on the other one... this should make the whole thing much quieter. And why the lows get better? I can't find an explaination. :bag:
Any idea?
 
#3
Uhm... the amp is a Peavey IPR1600. Honestly I can't hear distortion of any kind, the GP12 was bought NOS from a store and works perfectly... the sound is always very clean.
How a bandwidth limitation could cause this?
 
#4
The Peavey is certainly capable. Intermodulation distortion is not the kind of distortion you are probably thinking of. It is the ability to reproduce more than one frequency cleanly at the same time. I have the same power amps in my PA so that leaves the GP12 (NOS or not everything has design limitations that is reality not a "slam" on its quality) or the speaker cabs crossovers. Intermodulation distortion is not like an overdrive pedal's distortion character.

You asked and I answered. Bandwidth should not be confused with frequency response, if you limit the bandwidth to be handled into two pass bands accuracy improves. Think of it as multitasking (OVERLY simplified), a group of people can do only so many things well. Decrease the workload and output quality improves, increase the workload and quality or quantity suffers.
 
#5
I perfectly understand your explaination... but I'd expect this from (for example) a pair of 15"s (1way speakers). The fact these are 3ways cabs should NOT lead to that kind of intermodulation.
I have two Trace 1153T, they're full-range 15" cabs (no tweeter but they go up to 6khz). If I divided the workload between them, I'd certainly expect a better, cleaner sound. But not from cabs equipped with crossovers.
I'll have to doublecheck again how the sound changes with the two types of connection.
 
#7
I expected a drop of volume 'cause biamping I have one 15" reproducing the lows instead of 2 and one mid reproducing the highs (always instead of two).
The signal goes thru an active electronic crossover but also goes thru the passive crossover built into each cab.
 
#8
Sounds like the crossover points of your amp and your cabs aren't the same and you just happen to be more of a fan of the way the head's frequency ranges are dispersed over your cabs than the way each individual cab disperses the full range over itself.

IOW if a the crossover between the 15" and the 8" speakers is x and the biamp system crosses over at y < x the 15" in your "highs" cab will still be working a little bit, changing the voicing of the whole system.
 
  • Like
Reactions: Triad
#9
So there's no reason to expect a db loss? There's still one woofer pumping the lows instead of one. The crossover frequency on the Trace is set at 1khz if memory doesn't fail.
 
#10
English 2nd/3rd language?

I took you to be biamping both cabs with the power amp and Trace amp without any passive crossovers. You're going to have to spell out exactly what is going where.

Ordinary biamping of full range bass cabs nets a volume loss because the high cab is underused. No idea what you are doing.
 
#11
If you read carefully the original post, I stated "they have crossovers so when I biamp I should use something like the 15" on one and the mid/tweeter on the other one"...
 
#12
Try again friend, your grasp of English is not quite as good as your amping knowledge. At this point I still don't know what you're up to.

Cabs have passive crossovers which you must have removed from the signal chain to biamp.

You have 2 cabs, one biamping Trace preamp with mono amp onboard, and a Peavey DSP amp?

Correct me and fill in the rest plesse.
 
#13
LOL sorry but all the informations are in the first message... I didn't remove the crossovers, that's why I was expecting a volume loss biamping! :laugh:
The Peavey IPR1600 is stereo, as you can see looking at its specs and there's no mono amp involved... in fact I never mentioned it!
 
#14
OP, your explanations still leave us puzzled.
But please clarify your thinking:
- why "should" biamping lead to a volume loss?
- what does sounding "better" mean in this case? More SPL?

Anyway, the amplifier section in the Trace Elliot head is old school, and OLD (potentially no longer up to spec) and it probably uses the typical-for-its-time SJ50 / SK135 MosFets, which are not very "HiFi" devices in the applications they were usually put. The new Peavey amp is probably far more capable than the old TE amp.

Please read up on "intermodulation", too.
 
Last edited:
  • Like
Reactions: B-string
#16
Why "should" biamping lead to a volume loss?
Well, in this case 'cause I'd be using (on a pair of 3 ways cabinet with 15", 8" and tweeter) only the mids/highs of one cab and only the lows on the other one... this should make the stack less sensitive. But in reality I can't feel this volume loss. I checked though, the crossover was set at 250hz.

What does sounding "better" mean in this case? More SPL?
Nope, it sounded "fuller", with better lows (for some strange reason). The cabs aren't reverse in polarity, I hooked them together (in "stereo") and they work perfectly and move in the same direction.
I know the Trace preamp is based on 60s technology, though.

As I said, it's a bit strange and I was curious to find out the reasons. :)
 
#17
IF I've understood correctly, and I believe I have at this point, @Triad has two 3-way passive PA cabs (with internal passive crossovers to which he's done no modification, no bypassing, no nothing) and he's sending a low-passed signal to one cab and a hi-passed one to the other - just for shiggles and possibly gigs. ("[W]ired" meaning, in this interpretation, "cabled", connected to the amps, not "rewired each cab and provided it with separate jacks for bi-amp operation".)
His question is: why does this arrangement sound better, and especially not quieter, than amping both of them full-range? shouldn't the missing lows from the hi-passed cab...be missed?
Also, as @callofcthulhu pointed out: since they have passive xovers inside, depending on where the xover frequency is set on the Trace head with respect to that (the frequency) of the woof-to-mid internal one, either we have both woofers working (one only reproducing the upper part of its passband), or one of the mids is not reproducing the lower slice of what it usually does.
Jim Nazium said:
I wonder if the woofers on the two cabs have opposite polarity, i.e. they're 180 degrees out of phase with each other? If so, they'll tend to cancel each other out when run together. That might explain the increase in apparent low end when you bi-amp.
Click to expand...
+1, it occurred to me as well, definitely a possibility. (Oxymoron?) - EDIT: seems not.
 
#18
Exactly. But nope, they're not out of phase. I tried the cabs "in stereo" today and the volume seems to be the same... or if it's more, I can't really feel it. Maybe I should measure the dbs with a 100hz signal!
 
#19
Read my post about biamping full range bass cabs. If you set the crossover high then both cabs contribute lows. Otherwise you must expect a volume drop from half your low end production going away.

Better sound could come from using your electronic crossover in the Peavey.
 
#20
Not normally an easy thing to do, but now I guess I am confused as to what the question is and under what conditions? Do these speaker cabs have Biamp (separate high and low) input jacks along with full range inputs. Are the cabs identical and with no modifications (inspected for unmodified and no replacement drivers)?
 

Latest posts

Top Bottom
Back